Method for elongating foil

ABSTRACT

A method for elongating a foil, comprising steps of: providing an injection molding device, the injection molding device comprising a male mold having a projecting part protruding and a female mold defining a cavity; transmitting the foil into the injection molding device and between the male and female molds; clamping the male and female molds to form a molding space, the molding space being separated into a first airproof space adjacent to the female mold and a second airproof space adjacent to the male mold by the foil; vacuuming the first airproof space to suck the foil toward the first airproof space; and inputting thermal medium into the second airproof space to press the foil to cling to the inner surface of the cavity of the female mold.

Relevant subject matter is disclosed in the U.S. patent applications(application Ser. No. 11/956,345, still pending, and entitled “INJECTIONMOLDING DEVICE;” application Ser. No. 11/956,348, still pending, andentitled “METHOD FOR MANUFACTURING A FOIL DECORATED MOLDING;”application Ser. No. 11/956,349, still pending, and entitled “VALVEDEVICE OF INJECTION MOLDING DEVICE;” application Ser. No. 11/956,350,still pending, and entitled “INJECTION MOLDING DEVICE”), which are filedon the same date Dec. 14, 2007.

BACKGROUND

1. Field of the Invention

The present invention relates to a method for elongating a foil in aninjection molding device.

2. Description of Related Art

Conventionally, various kinds of methods for manufacturing a foildecorated molding, which is molded by an injection molding process andhas a transfer layer removed from a substrate foil of a transfer foiland placed on the surface of the molding after the transfer foil isinserted into cavities in an injection mold, have been known in the art.Since the use of the method requires an alignment of the transfer foilalong a cavity-forming face of the mold, the transfer foil is preheatedbefore the injection molding process so as to be easily aligned alongthe cavity-forming face of the mold where the cavity-forming facethereof is greatly recessed or projected from a parting face of themold.

A traditional injection molding method includes transferring a heaterbetween the male mold and the female mold to heat the foil beforematching the molds, and removing the heater after the foil is heated.However, because of the need for the heater and the space it occupies,cost and volume of the injection mold is increased.

What is needed is to provide an effective method for elongating a foilin an injection molding device.

SUMMARY

In one embodiment, a method for elongating a foil, comprising steps of:providing an injection molding device, the injection molding devicecomprising a male mold having a projecting part protruding and a femalemold defining a cavity; transmitting the foil into the injection moldingdevice and between the male and female molds; clamping the male andfemale molds to form a molding space, the molding space being separatedinto a first airproof space adjacent to the female mold and a secondairproof space adjacent to the male mold by the foil; vacuuming thefirst airproof space to suck the foil toward the first airproof space;and inputting thermal medium into the second airproof space to press thefoil to cling to the inner surface of the cavity of the female mold.

Other advantages and novel features of the present invention will becomemore apparent from the following detailed description of an embodimentwhen taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an injection molding deviceactualizing a method for elongating a foil in accordance with anembodiment of the present invention, the injection molding deviceincluding a male mold and a female mold;

FIG. 2 is a cross-sectional view of the female mold, similar to FIG. 1;

FIGS. 3 and 4 are enlarged, partially cutaway views of the male mold ofFIG. 1, showing two using states respectively;

FIG. 5 is a cross-sectional view of the female mold of FIG. 1, butshowing the foil extending into the cavity of the female mold;

FIG. 6 is similar to FIG. 1, but showing the foil extending along aninner surface of the cavity of the female mold and the male and femalemolds matched together;

FIG. 7 is similar to FIG. 6, but showing a state after injection; and

FIG. 8 is a flow chart of the method for elongating the foil.

DETAILED DESCRIPTION

Referring to FIG. 1, an injection molding device actualizing a methodfor elongating a foil in accordance with an embodiment of the presentinvention is provided for elongating a foil 100. The injection moldingdevice includes a transport 10, a mold including a male mold 20 and afemale mold 30, a plurality of pressing members 40, and a thermal mediumsource 90.

The male mold 20 forms a projecting part 21 protruding toward the femalemold 30. A plurality of air discharging holes 23 is defined in the malemold 20 around the projecting part 21 and extending from a side, facingthe female mold 30, of the male mold 20 to an opposite side of the malemold 20. A pressure release valve 80 is connected to each airdischarging hole 23. The pressure release valve 80 is adjustableaccording to need during molding. A plurality of receiving slots 25 isdefined in the male mold 20 in vicinity of edges of the male mold 20. Aplurality of hermetic rings 27 is received in the correspondingreceiving slots 25.

Referring to FIG. 2, the female mold 30 defines a cavity 31 therein. Thecavity 31 includes a bottom surface A3, a first side surface A1extending from an edge of the bottom surface A3 and a second sidesurface A2 extending from an opposite edge of the bottom surface A3 to asurface that faces the male mold 20, with an opening formed on thecorresponding surface of the female mold 30. A length of the opening ofthe cavity 31 is L. A plurality of air discharging holes 32 is definedin the male mold 20 and extending from a side, facing the male mold 20,of the female mold 30 to an opposite side of the female mold 30. Atleast two of the air discharging holes 32 extend from the bottom surfaceA3 of the cavity 31 to the corresponding side of the female mold 30opposite to the male mold 20. Each air discharging hole 32 is connectedto a vacuum pump at the side of the female mold 30 opposite to the malemold 20. A plurality of hermetic rings 33 is attached to the female mold30 adjacent to an edge of the female mold 30.

Referring also to FIGS. 3 and 4, the male mold 20 defines a plurality ofchannels 29 therein extending from a side, facing the female mold 30, ofthe projecting part 21 to a side of the male mold 20 opposite to thefemale mold 30. Each channel 29 includes a bell-mouthed recessed portion291 defined in the projecting part 21 with a large end thereof in thesurface facing the female mold 30, of the projecting part 21, a conduit295 defined in the male mold 20 communicating with a small end of therecessed portion 291, and an L-shaped slender duct 296 with one endcommunicating with the conduit 295 and the other end passing through thesurface opposite to the female mold 30, of the male mold 20. A block 298protrudes in from one end opposite to the recessed portion 291, of theconduit 295. One end of a pipe 91 is connected to the end opposite tothe female mold 30, of each slender duct 296, and the other end of thepipe 91 is connected to the thermal medium source 90. A through hole isdefined in the block 298.

A plug 70 is attached in each channel 29. The plug 70 includes ataper-shaped obturating portion 71 for obturating the recessed portion291 of the channel 29, and a pole 73 extending from a small end of theobturating portion 71. The pole 73 extends through the through hole ofthe block 298. A fastening member 75 is fixed to a distal end of thepole 73. A resilient member 79, such as a spring, fits about the pole 73and is resiliently located between the block 298 and the fasteningmember 75.

The thermal medium source 90 has thermal medium contained therein, suchas thermal liquid or high-pressure gas. In this embodiment, the thermalmedium is thermal high-pressure gas. The thermal medium is capable ofbeing heated by an electric heater or an infrared ray heater (IRheater).

The transport 10 includes two transporting rollers 13 and two guidingrollers 15 positioned at two opposite ends of the mold respectively, fortransporting the foil 100 into the mold. The foil 100 includes a baselayer, and a printed layer attached to the base layer and having printedpatterns or characters.

Referring also to FIG. 8, the method includes the following steps. Thefoil 100 is transported into the mold between the male and female molds20, 30. The male, female molds 20, 30, and the pressing members 40 areclamped together to form a molding space among an inner surface of thecavity 31 of the female mold 30, the projecting portion 21 of the malemold 20, and parts around the projecting portion 21. The pressingmembers 40 are received in the corresponding receiving slots 25 of themale mold 20, and press the corresponding hermetic rings 27, 33 toairproof the molding space. The molding space is separated into a firstairproof space adjacent to the female mold 30 and a second airproofspace adjacent to the male mold 20 by the foil 100. The vacuum pump isconnected to the air discharging holes 32 of the female mold 30 tovacuumize the first airproof space, thus the foil 100 is sucked towardthe first airproof space, as shown in FIG. 5. The pressure release valve80 is shut, and the value of the pressure release valve 80 ispredetermined according to the molding condition. The thermal mediumsource 90 inputs heated gas to the channels 29 via the pipes 91. Theplugs 70 are driven by the heated gas to move toward the female mold 30,therefore the channels 29 open. The heated gas is blown into the secondairproof space to press the foil 100 to cling to the inner surface ofthe cavity 31 of the female mold 30. The foil 100 is intenerated by theheated gas to cling to the inner surface of the cavity 31 easily, asshown in FIG. 6.

Referring also to FIG. 7, molten resin is injected through an injectionopening defined in the male mold 20 into the molding space. The moltenresin presses the plugs 70 into the corresponding channels 29 againstresistance of the corresponding resilient members 79. The heated gas inthe second airproof space is released via the air discharging holes 23of the male mold 20 when the pressure in the molding space is greaterthan the predetermined value of the pressure release valve 80. Themolten resin is cooled to form a mold body. The mold is opened, with themale mold 20 being separated from the female mold 30. The base layer ofthe foil 100 is released from the mold body. Thus, the printed layer ofthe foil 100 is attached to a surface of the mold body.

In this embodiment, the injection molding device is used for elongatingthe foil 100 between the male and female molds 20, 30 by exhausting airfrom the cavity 31 via the air discharge holes 32 of the female mold 30and pressurizing the foil 100 via the heated gas. For example, a lengthof the first side surface A1 is a1, a length of the second side surfaceA2 is a2, and a length of the bottom surface A3 is a3, when the first,second, and bottom surface A1, A2, A3 of the cavity 31 and the length Laccord with an expressional a1+a2+a3>=(1+20%)*L, the foil 100 is capableof being elongated for suiting the cavity 31 of the female mold 30.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size, and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

1. A method for elongating a foil, comprising steps of: providing aninjection molding device, the injection molding device comprising a malemold and a female mold, the male mold having a projecting pan protrudingtoward the female mold, the female mold defining a cavity correspondingto the projecting part, a channel defined in the male mold, a plugresiliently attached and movable in the channel for obturating therecessed portion of the channel and is capable of opening or closing thechannel automatically; transporting the foil into the injection moldingdevice between the male and female molds; clamping the male and femalemolds to form a molding space surrounded by an inner surface of thecavity of the female mold, the projecting part, and parts around theprojecting part of the male mold, the molding space being separated intoa first airproof space adjacent to the female mold and a second airproofspace adjacent to the male mold by the foil; vacuuming the firstairproof space to suck the foil toward the first airproof space; andinputting thermal medium into the second airproof space through thechannel to press the foil to cling to the inner surface of the cavity ofthe female mold.
 2. The method as claimed in claim 1, wherein thechannel extends from a side, facing the inner surface of the cavity ofthe female mold, of the projecting part of the male mold to a side,opposite to the projecting part, of the male mold.
 3. The method asclaimed in claim 2, wherein the thermal medium is capable of driving theplug to open the channel.
 4. The method as claimed in claim 2, whereinthe thermal medium is produced by a heater connected to the channels. 5.The method as claimed in claim 4, wherein the heater is an electricheater or an infrared ray heater.
 6. The method as claimed in claim 1,wherein the thermal medium is heated gas, an air discharging hole isdefined in the male mold for releasing the heated gas from the malemold.
 7. The method as claimed in claim 6, wherein a pressure releasevalve is connected to the air discharging hole for maintaining apredetermined pressure in the mold.
 8. The method as claimed in claim 1,wherein a vacuum pump is connected to the female mold to vacuumize thefirst airproof space.
 9. A method for elongating a foil, comprisingsteps of: providing an injection molding device, the injection moldingdevice comprising a male mold and a female mold, the male mold having aprojecting part protruding toward the female mold, the female molddefining a cavity corresponding to the projecting part, a channeldefined in the male mold, a plug received in the channel and movabletoward or away from the female mold for opening or closing the channel;transporting the foil into the injection molding device end between themale and female molds; locking the foil to the female mold to form anairproof space together with the cavity of the female; vacuuming theairproof space to suck the foil toward the female mold; clamping themale and female molds to form a molding space; and inputting thermalmedium into the channel, the thermal medium driving the plug to movetoward the female mold to open the channel thus the thermal mediumblowing into the molding space to press the foil to cling to an innersurface of the cavity of the female mold.
 10. The method as claimed inclaim 1, wherein the channel comprises a bell-mouthed recessed portiondefined in the projecting part with a large end thereof facing thefemale mold, the plug comprises a taper-shaped obturating portion forobturating the recessed portion of the channel to open or close thechannel.
 11. The method as claimed in claim 10, wherein the plug furthercomprises a pole extending from a small end of the obturating portion, ablock protrudes into the channel from one end opposite to the recessedportion, a through hole is defined in the block, the pole extendsthrough the through hole of the block, a fastening member is fixed to adistal end of the pole, a resilient member fits about the pole and isresiliently located between the block and the fastening member.
 12. Themethod as claimed in claim 9, wherein the channel comprises abell-mouthed recessed portion defined in the projecting part with alarge end thereof facing the female mold, the plug comprises ataper-shaped obturating portion for obturating the recessed portion ofthe channel to open or close the channel.
 13. The method as claimed inclaim 12, wherein the thermal medium drives the obturating portion ofthe plug to move toward the female mold away from the recessed portionof the channel.
 14. The method as claimed in claim 12, wherein the plugfurther comprises a pole extending from a small end of the obturatingportion, a block protrudes into the channel from one end opposite to therecessed portion, a through hole is defined in the block, the poleextends through the through hole of the block, a fastening member isfixed to a distal end of the pole, a resilient member fits about thepole and is resiliently located between the block and the fasteningmember.